Polyamide-imide solution and polyamide-imide film

Abstract

An object of the present invention is to obtain a polyamide-imide solution that has a low linear thermal expansion coefficient, that is, an excellent linear thermal expansion coefficient, and that also is excellent in coating applicability. A further object of the present invention is to provide, with use of the polyamide-imide solution, a product or member which has high requirements for heat resistance and a low linear thermal expansion coefficient. In particular, the present invention is intended to provide a product or member that is suitably used for applications in which the polyamide-imide film obtained from the polyamide-imide solution of the present invention is formed on a surface of an inorganic material such as metal, metal oxide, or monocrystalline silicon. The above objects can be achieved by a polyamide-imide solution including: a specific polyamide-imide; and an organic solvent, the organic solvent being a mixture solvent of an amide solvent and a non-amide solvent, the non-amide solvent being at least one solvent selected from the group consisting of ether solvents, ketone solvents, ester solvents, glycol ether solvents, and glycol ester solvents.

1 . A polyamide-imide solution comprising:
 an organic solvent; and   a polyamide-imide including a structure represented by the general formula (1):   
       
         
           
           
               
               
           
         
         the organic solvent being a mixture solvent of an amide solvent and a non-amide solvent, 
         the non-amide solvent being at least one solvent selected from the group consisting of ether solvents, ketone solvents, ester solvents, glycol ether solvents, and glycol ester solvents. 
       
     
     
         2 . The polyamide-imide solution as set forth in  claim 1 , wherein a weight ratio of the amide solvent and the non-amide solvent (amide solvent/non-amide solvent) is in a range of 80/20 to 5/95. 
     
     
         3 . The polyamide-imide solution as set forth in  claim 1 , wherein:
 the polyamide-imide including the structure represented by the general formula (1) is a polyamide-imide represented by the general formula (6):   
       
         
           
           
               
               
           
         
       
     
     
         4 . The polyamide-imide solution as set forth in  claim 1 , wherein:
 the amide solvent is N,N-dimethylacetamide or N,N-dimethylformamide; and   the non-amide solvent is at least one solvent selected from the group consisting of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, propyleneglycol monomethylether acetate, methyl triglyme, methyl tetraglyme, methyl monoglyme, methyl diglyme, ethyl monoglyme, ethyl diglyme, butyl diglyme, and γ-butyrolactone.   
     
     
         5 . A polyamide-imide film comprising a polyamide-imide including a structure represented by the general formula (1): 
       
         
           
           
               
               
           
         
         the polyamide-imide film having a birefringence ΔN of 0.040 or higher, 
         the birefringence being expressed by ΔN=Nxy−Nz, where Nxy is an in-plane refractive index and Nz is a refractive index in a thickness direction. 
       
     
     
         6 . A polyamide-imide film obtained by forming a film from a polyamide-imide solution as set forth in  claim 1 . 
     
     
         7 . The polyamide-imide film as set forth in  claim 5 , obtained by forming a film from a polyamide-imide solution,
 the polyamide-imide solution including:   an organic solvent; and   a polyamide-imide including a structure represented by the general formula (1),   the organic solvent being a mixture solvent of an amide solvent and a non-amide solvent,   the non-amide solvent being at least one solvent selected from the group consisting of ether solvents, ketone solvents, ester solvents, glycol ether solvents, and glycol ester solvents.   
     
     
         8 . The polyamide-imide film as set forth in  claim 6 , obtained by applying the polyamide-imide solution onto a support. 
     
     
         9 . The polyamide-imide film as set forth in  claim 5 , having a linear thermal expansion coefficient of 22 ppm/K or less at a temperature in a range of 100° C. to 300° C. 
     
     
         10 . The polyamide-imide film as set forth in  claim 5 , wherein:
 the birefringence ΔN is 0.070 or more and 0.30 or less,   the birefringence ΔN being expressed by ΔN=Nxy−Nz, where Nxy is an in-plane refractive index and Nz is an refractive index.   
     
     
         11 . A laminate comprising:
 a polyamide-imide film as set forth in  claim 5 ; and   a glass substrate.   
     
     
         12 . A flexible display substrate comprising a polyamide-imide film as set forth in  claim 5 . 
     
     
         13 . A TFT substrate comprising a polyamide-imide film as set forth in  claim 5 . 
     
     
         14 . A color filter comprising a polyamide-imide film as set forth in  claim 5 . 
     
     
         15 . An electronic paper comprising a polyamide-imide film as set forth in  claim 5 . 
     
     
         16 . An organic EL display comprising a polyamide-imide film as set forth in  claim 5 . 
     
     
         17 . The polyamide-imide film as set forth in  claim 7 , obtained by applying the polyamide-imide solution onto a support. 
     
     
         18 . The polyamide-imide film as set forth in  claim 6 , having a linear thermal expansion coefficient of 22 ppm/K or less at a temperature in a range of 100° C. to 300° C. 
     
     
         19 . The polyamide-imide film as set forth in  claim 6  wherein:
 the birefringence ΔN is 0.070 or more and 0.30 or less, 
 the birefringence ΔN being expressed by ΔN=Nxy−Nz, where Nxy is an in-plane refractive index and Nz is an refractive index.